The monsoon has once again run into a brief lull after winds erred in direction and speed, but numerical weather prediction models indicated that the rains would revive from Wednesday.

The offshore trough from south Konkan-Goa persisted but the westerly to southwesterlies tended to become westerly to northwesterlies on approach except over the southern tip of the peninsula.STRAYING WINDS

A prevailing western disturbance and its band of northwesterlies seemed to have entrenched itself down to central India and beyond, forcing the southwesterlies to stray.

But this would trigger isolated rain or thundershowers over Jammu and Kashmir, Himachal Pradesh and Uttarkhand. Isolated dust storm or thunderstorm has been forecast over Rajasthan.

Convective clouds were seen over east-central and adjoining southeast Arabian Sea, besides over north Andaman Sea and north and adjoining central Bay of Bengal across the peninsula, the IMD update said.

The Chennai Met Centre said that the monsoon was vigorous over north interior Karnataka and active over Kerala during the 24 hours ending Monday morning.

Forecast for the next two days, however, indicated the possibility of thundershowers at many places over Kerala, Lakshadweep and coastal Karnataka, and at a few places over interior Karnataka. Isolated rain or thundershowers have been forecast for Tamil Nadu, Puducherry and Andhra Pradesh.

A warning valid for the period said that isolated heavy rain is likely over Kerala and coastal Karnataka.WAIT FOR MUMBAI

Latest forecast from the International Research Institute (IRI) at Columbia University suggests that the monsoon may not enter Mumbai until sometime after the June-10 normal.

The erratic rains are now expected to enter the metropolis around June 13 only, although occasional pre-monsoon showers are likely to occur during the run-up to this.

In fact, the IMD has said that rain or thundershowers are likely at a few places over Konkan and Goa, while being isolated over south Madhya Maharashtra over the next few days.BAY ACTIVITY

The European Centre for Medium-Range Weather Forecasts (ECMWF) has assessed that the Bay of Bengal may be readying itself to host a typical monsoon ‘low’ from June 15 onwards.

The system might show up to northwest of Andaman and Nicobar Islands and might get embedded in a larger trough of low-pressure area during the next two to three days.

This is more or less corroborated by precipitation forecasts made by the US National Centres for Environmental Prediction (NCEP) showing gains for the west coast and the rest of the peninsula from June 16 to 24.

Convection is shown to spread from southeast to northeast Arabian Sea during this phase when rains would have covered the entire west coast. The Bay ‘low’ might spearhead rains into the peninsulas and set up an interaction with a counterpart to the west.